All of these improvements shouldn’t obscure the fact that the potential of carbon capture is limited. Carbon capture and storage will never be able to accommodate all of the carbon dioxide we emit now. And quite frankly, carbon capture would have trouble just keeping up with the increase in coal consumption (see “The Enduring Technology of Coal”).

Capturing and storing carbon dioxide will always make electricity more expensive. It will always be cheaper just to let the carbon dioxide escape into the atmosphere.

Even if costs are made far lower than they are today, the impact of carbon capture will be limited by the sheer scale of infrastructure needed to store carbon dioxide. During combustion, each carbon atom from coal combines with two atoms of oxygen from the air, and this creates a huge amount of stuff. Even once the gas has been compressed into a liquid that can be piped to storage sites, the volume is immense.

Vaclav Smil, a professor at University of Manitoba and master of sobering energy-related numbers, calculates that if we were to bury just one-fifth of the global carbon dioxide emissions, we would need to build an industry capable of handling twice the volume of stuff as the entire oil industry, an industry that took 100 years to develop, driven by a large and mostly expanding market.

In some cases, at a limited scale, the cost of capturing carbon dioxide will be low enough (as it is now for capturing it from some industrial sources) that it can be sold for a profit for some applications. Future reductions in costs could expand these applications. But the market for carbon dioxide will be limited.

One market is for enhanced oil recovery; that is, injecting carbon dioxide into oil wells to increase the amount of oil they can produce. The carbon dioxide would stay underground. In some cases, this technique could double the amount of oil that comes out of a well. And, of course, burning that oil emits a fair amount of carbon dioxide. If enhanced oil recovery lowers the cost of oil and boosts demand, that could offset at least some of the gains from storing the carbon dioxide in the wells.

Incidentally, other technologies for reducing carbon dioxide emissions also run into trouble at large scales. Solar power can compete in some places in the world without subsidies today. But its cost will go up at large scales as the intermittency of the source becomes a burden to the grid, and as ever-larger backup supplies of power (other power plants or energy storage) are needed for power at night or during days or weeks when there isn’t much sunshine.

Carbon capture technology can reduce the overall cost of cutting carbon dioxide emissions. It can allow us to continue using some of the fossil fuel infrastructure that’s been built to power civilization. But it isn’t a panacea. We’d still need to rely heavily on other technologies—such as efficiency-related technology, renewables, and nuclear—if we were to create a low-carbon economy.